Credit

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Caption

Optical photo of the double star Alpha Centauri, the third brightest star in the sky. The pair (A, upper left, & B, lower right), along with a faint companion known as Proxima Centauri, form the nearest known star system to our own, at a distance of only 4.3 light years. Alpha Centauri A & B are about 20 arc seconds apart & orbit each other once every 80 years. The faint companion, Proxima Centauri, is the closest of the three to us. It is located over two degrees away from Alpha Centauri (out of the frame of this photo) & orbits the pair with a period of millions of years.